1. Field of the Invention
The present invention pertains to airguns and more particularly to a gas expansion chamber for use with carbon dioxide powered airguns.
2. Background Art
The advantages of the use of carbon dioxide gas as a propellant in airguns is a well known and accepted practice. Such carbon dioxide gas is generally stored in a liquid state. Inasmuch as most airguns perform best when the propellant that is used is exclusively in a gaseous state, the actual product delivered from high pressure carbon dioxide (CO2) storage vessels is a variable mixture of liquid and gaseous CO2. The liquid content of CO2 within a storage vessel creates a problem. The liquid to gas proportion of the mix varies depending upon the attitude or position of the storage vessel, as well as such things as the amount of agitation caused by handling of the airgun or the storage vessel and also ambient temperature conditions.
In addition to the problems caused by liquid CO2 as outlined above, an additional problem referred to as "aerosol supercharging" frequently exists. Aerosol supercharging occurs when the airgun ingests a propellant mix that consists of gaseous CO2 with droplets of liquid CO2 suspended within the gas stream. With this mixture present in the valve chamber of an airgun, the droplets can, depending upon variables like temperature and rate of fire, convert to a gaseous state and thereby substantially elevate pressure within the valve chamber. Such increases in pressure create unacceptable velocity variations and may also result in both poor accuracy and unsafe operating conditions.
An attempt at solving this problem has been met by some individuals installing long lengths of high pressure hose between the supply vessel and the valve chamber of the airgun. The theory being that the liquid CO2 transversing the length of the hose will make the transition from a liquid to a gaseous state. It has been generally found and accepted that this approach to the problem has been largely ineffective inasmuch as substantial amounts of liquid CO2 still are able to enter the valve chamber of the airgun.
Other efforts to deal with the problem have involved remounting a supply vessel into particular orientations that are intended to minimize the amount of liquid propellant that exits in the supply vessel. Such attempts have frequently created relationships between the airgun and supply vessel combination that ergonomically or aesthetically are unacceptable or undesirable.
In a search of the background art directed to the subject matter of the present invention conducted in the U.S. Patent and Trademark Office, no patents were found relating to the use of expansion chambers for carbon dioxide powered airguns. The only expansion chamber found was included in a process and apparatus for producing and using cold ammonia as a fertilizer as taught in U.S. Pat. No. 4,069,029 which issued on Jan. 17, 1978 to John William Hudson. This patent teaches the introduction of a stream of ambient temperature pressurized liquid ammonia at high velocity into an expansion chamber. A mist eliminator located within the expansion chamber eliminates suspended droplets of cold liquid ammonia in the cold gaseous ammonia stream passing into the chamber. Hudson teaches the use of a stationary blade as a mist eliminator because of its inherent simplicity, compactness and light weight. After a thorough review of the above identified patent, it is believed that it neither teaches, discloses or claims the novel combination of elements and functions found in the improved airgun expansion chamber taught by the present invention.